ROS2 SH can only use ROS1 mix files and types.

[russkel]

The tests are not testing ROS2 SH correctly.

I have been debugging the following errors for a while trying to figure out why these would pass on CI but not on my computer:

[Integration Service][INFO] [is::sh::ROS2] Created node '/is_ros2_node_1804289383' with Domain ID: 0
[Integration Service][ERROR] [is::sh::ROS2] Could not find .mix file for message type: 'std_msgs/String'.
 -- Make sure that you have generated the 'is-ros2' extension for that message type by calling 'is_ros2_rosidl_mix(PACKAGES <package> MIDDLEWARES ros2)' in your build system!
[Integration Service][ERROR] [is::core::InstanceHandle] Failed to load middlewares!

When generating the mix lib for std_msgs as ROS2 the cmake files will put the mix file in:

./install/is-ros2-mix-generator/lib/is/ros2/msg/std_msgs/msg/Int16.mix
./install/is-ros2-mix-generator/lib/is/ros2/msg/std_msgs/msg/Int64.mix
./install/is-ros2-mix-generator/lib/is/ros2/msg/std_msgs/msg/Int32.mix
./install/is-ros2-mix-generator/lib/is/ros2/msg/std_msgs/msg/Byte.mix

However, in utils/ros2-mix-generator/resources/convert__msg.hpp.em the msg_type_string is set to std_msgs/Int16, so it will never be discovered if using ROS2 only:

[Integration Service][INFO] [is::sh::ROS2] Created node '/is_ros2_node_1804289383' with Domain ID: 0
[Integration Service][ERROR] [is::sh::ROS2::Factory] 'create_type' could not find a factory type named 'std_msgs/msg/String' to create!
[Integration Service][ERROR] [is::sh::ROS2] Failed to register the required DynamicType 'std_msgs/msg/String'
[Integration Service][ERROR] [is::core::InstanceHandle] Failed to load middlewares!

The only reason this is passing in tests is the ROS1 interfaces are installed and it's using those DynamicTypes!